Written by Danielle Bubole

Edited and Reviewed by Reuben J C. Los Baños, Ph.D.

The Golgi apparatus is the collecting, sorting, and packaging site of your cell. These packaged and sorted materials are then delivered to different sites for daily use. Thus, your Golgi apparatus’ main function is arranging collected cellular materials and putting them inside a vesicle to be delivered and used to different sites.

It’s either delivered to:

• The outside of your cell (through exocytosis)
• Endosomes make it into lysosomes
• Other cytoplasmic components

Exocytosis is the process of getting stuff outside of the cell.

Endocytosis is the process of getting stuff into the cell.

Now that you have a grasp of the overview of your Golgi apparatus’ function, let’s learn its main components.

Similar to your organ system which consists of collaborating organs, your Golgi apparatus also has its own components, these are:

• Cisternae – smooth membrane sac that forms the flat discs with swollen ends of your Golgi apparatus.
• Tubules – short interconnected structures protruding on the sides and also at a part of your Golgi apparatus that faces your cell membrane.
• Vesicles – sacs that develop from your tubules.
• Golgi vacuoles – large rounded sacs produced from a part of the Golgi apparatus that faces your cell membrane. Sometimes, it also acts as a lysosome.
• ERGIC – also called as Endoplasmic Reticulum Golgi Intermediate Compartment helps in the transport between your ER and Golgi apparatus.

Moving on to its networks, your Golgi apparatus is also divided into clusters of cisternae called:

• The convex cis face or the forming face (cis-Golgi Network)
• The concave trans face or the maturing face (trans-Golgi Network)

Forming face is what is near your endoplasmic reticulum and the primary site to receive the materials in the vesicles from your ER.

Maturing face is what is near your cell membrane and the site where the vesicles to be delivered in other sites are pinched out.

You must keep these in mind as we go into its process.

Remember that the proteins and lipids or the materials made by your ER are packaged in the form of vesicles. With the help of ERGIC, these vesicles will fuse with your forming face of your Golgi apparatus and move toward your maturing face. At the maturing face, the vesicle with the sorted and modified materials inside is pinched out to be delivered outside of the cell, fused with endosomes to make lysosomes, and delivered to other cytoplasmic components.

All in all, that is how your Golgi apparatus works. However, to know more let’s dive deeper!

What is the function of the Golgi vesicles?

Golgi vesicles are small sacs that develop from tubules. Your Golgi apparatus’ vesicles help the transport of materials from one place to another. It encloses it, acting like a barrier from other cytoplasmic components.

There are two types of Golgi vesicles, namely:

• smooth vesicles
• coated vesicles

Different types of Golgi vesicles also have specific different functions. Let’s take a look at what these two types have.

Smooth vesicles

• Does not have a protein coat
• Transport materials inside your Golgi apparatus, to the plasma membrane, and other organelles
• Your smooth vesicles include secretory vesicles and other Golgi transport vesicles

Examples of your smooth vesicles are:

• Secretory vesicles (those that release hormones and neurotransmitters)
  • Transport vesicles inside your Golgi apparatus
  • Lipid-containing vesicles
• Their release mechanism can be constitutive (constant release) or regulated (stimulus-dependent release)

Coated Vesicles

• Covered with a proteinaceous coat (COPI, COPII, clathrin)
• Helps in your sorting, packaging, and transport of materials by selecting specific molecules
• Your coated vesicles include COPI, COPII, and clathrin-coated vesicles:
  • COPI-coated vesicles: retrograde transport in Golgi; it helps return proteins that accidentally left the ER.
  • COPII-coated vesicles: ER to Golgi transport
  • Clathrin-coated vesicles: transport materials from your Golgi to the endosome, which also involved in endocytosis
• Your coat assists in the selection of materials and budding of your vesicle. It is also removed before fusing with the target site.

Therefore, your type of vesicle relies on what appearance it has, whether it is coated or not. If it is coated what type of protein coat is present?

What is the role of the Golgi body in secretion?

Golgi body or Golgi apparatus transports modified materials to different sites. It includes delivering materials inside a vesicle outside of the cell. Thus, this is what you can call an example of secretion.

Back to your knowledge of cells, your cells produce proteins. For example, your nerve cell produces neurotransmitters, pituitary cells produce peptide hormones, and beta cells secrete insulin.

What do these have in common? Your secretory vesicles

There are two types of secretion, namely:

• Constitutive secretion – vesicles from the mature face are sent to the cell’s membrane for continued secretion
• Regulated secretion – vesicles containing the materials for secretion remain on the cell’s surface and wait for the signal to be secreted.

Now that you are set with this information, let us look more at its process.

Imagine the pancreatic beta cell, in these beta cells vesicles are filled with your insulin that is then modified and pinched out as a vesicle from the mature face of your Golgi apparatus.

Vesicles containing the same materials will fuse forming larger secretory vesicles. Those vesicles that contain insulin build up in the cell and wait for a glucose signal to enter the cell.

Once the glucose arrives, it will start a complicated process that causes the release. In a sense, it is not freed up because of glucose itself but because of the complicated process caused by the presence of glucose.

The secretory vesicles that contain the materials, insulin, will move to the plasma membrane and release the materials to neighboring blood capillaries. This process along with regulated release is what you call exocytosis.

Your released insulin will now act as a regulator that stimulates others.

In summary, Golgi body forms the vesicle for the materials needed to be secreted outside the cell or transported to different cytoplasmic components.

Where is the Golgi apparatus located?

Your Golgi apparatus is a membrane-bound organelle found in eukaryotic cells. It is located near the endoplasmic reticulum and nucleus.

Essentially, Golgi apparatus works very often with your endoplasmic reticulum. The materials made by your ER are transported via the vesicles to your Golgi body then sorted, modified, and packed to deliver into different sites. This explains why the Golgi apparatus remains close to the endoplasmic reticulum.

Secretory cells, those cells that the major function is to secrete contain many Golgi apparatus, however, no matter how many of them, these are still located in close proximity to your ER.

If you get into detail:

• Convex cis face or the forming face – is located near the ER.
• Medial Section – is located in the middle of the forming face and maturing face.
• Concave trans face or the maturing face – is located far from the ER and much closer to the cell membrane compared to your forming face.

Note: this is not to be confused with the Golgi network. Your Golgi networks are two clusters of cisternae namely the cis-Golgi Network and trans-Golgi Network. While the Convex cis face or the forming face, the Medial Section, and the Concave trans face or the maturing face are the regions.

Cisternae is divided into networks that are composed of regions containing different components such as your cisternae, golgi tubules, golgi vesicles, golgi vacuoles, and ERGIC. In summary, your Golgi apparatus is located near your ER to facilitate efficient transport of materials from your ER to the forming face towards the maturing face through the medial section.

Your network’s location is dependent on its function such as to receive or to secrete vesicles.

What would happen to the life of a cell if there was no Golgi apparatus?

Your cells produce proteins. Nerve cell produces neurotransmitters, pituitary cells produce peptide hormones, and beta cells secrete insulin. These are all products of your Golgi apparatus’ work.

Golgi apparatus collects, sorts, and packages materials to be brought to different sites via vesicles. Many of your proteins are synthesized by ribosomes in the endoplasmic reticulum, these are transported to your forming face and then modified before the vesicle containing these materials is pinched out from the mature face of your Golgi apparatus.

Your vesicles containing the materials modified from your Golgi apparatus move and fuse to larger secretory vesicles containing the same materials. These build up until it is secreted. Your cells’ secretion via Golgi apparatus is very important because it stimulates other molecules, and in turn responds to them, contributing to the overall process of the body.

Aside from getting the materials outside of the cell, vesicles from the mature face are delivered to either the endosomes to form lysosomes and other cytoplasmic components.

Your Golgi apparatus, Endoplasmic reticulum, and endosomes work in harmony. ER produces vesicles containing the materials transported to the Golgi apparatus which is then modified. Your modified materials are delivered outside of the cell for extracellular needs or add up to the cell membrane, and they can be transported to the endosomes to help produce the lysosomes.

Lysosomes are your cells’ site of digestion. It contains digestive enzymes, specifically hydrolytic ones. It breaks down wasted or worn-out cell parts, destroys viruses and bacteria, and ultimately, performs cell death if a cell is beyond repair to eliminate unwanted cells.

Therefore, if your Golgi apparatus is absent in your cell, there will be no means of transportation for secreting materials outside of your cell or exocytosis, no production of lysosomes, and no delivery of needed materials to other cytoplasmic components.

All in all, your cell will eventually DIE!

Who discovered the Golgi apparatus?

Golgi apparatus was discovered by Camillo Golgi. He is an Italian cytologist who discovered Golgi apparatus in a nerve cell of an owl.

Studying the nervous tissue, Camillo established a staining technique. This technique is named reazione nera, which means “black reaction.” In the present, it is known as the Golgi Stain. His way of staining includes fixing the nervous tissue with potassium dichromate and bathing it with silver nitrate.

While studying neurons using his technique, he identified an “internal reticular apparatus” and then later on called the Golgi Apparatus.

Camillos’ finding of this structure was doubted by other scientists but then during the invention of your electron microscope, Golgi Apparatus was confirmed to be real.

His findings not only contributed to scientific innovation but also led many medical developments to emerge, particularly in cell biology, neuroscience, and disease and research.

What are some interesting facts about the Golgi apparatus?

Golgi contains about 1,000 different proteins in mammalian cells, however, only 200 of them have been identified as of now.

Having 1,000 different kinds of protein only suggests that a very small component can do so much such as:

• Glycosylation – helps in protein folding, protects proteins from damage, and enables cell signaling and communication. (Example: The difference in blood types is due to different glycosylation patterns on red blood cells.)
• Processing hormones and neuropeptides – most hormones and neurotransmitters function after it is cut and activated. (Example: Insulin is also processed by your Golgi apparatus, which is important for your blood sugar regulation and preventing diabetes.)
• Transporting and sorting proteins – transports your proteins to specific locations and avoids misplacement that can cause diseases. (Example: Genetic disorders like I-cell or the build-up of waste in the cell will happen if lysosomal enzymes are not sent to lysosomes.)
• Making and modifying lipids – Production of your lipids for cell membranes and signaling molecules. (Example: Your sphingolipids are made by your Golgi apparatus, this is important for brain function and nerve protection.)
• Moving ions and molecules across membranes – supports your cell balance and metabolism for cell survival. (Example: Wilson’s disease can occur if mutations in copper-transporting proteins happen. This is caused by the build-up of copper in the body.)
• Maintaining Golgi structure – it keeps your Golgi apparatus organized so materials can be processed correctly and delivered to where it is needed. (Example: Disruptions of your Golgi apparatus can cause cancer and neurodegenerative diseases.)
• Connecting to the cytoskeleton – helps in cell division, immune response, and nerve function. (Example: Movement of your Golgi apparatus is needed for the release of your immune cells to targeted directions, fighting infections.)

Therefore, your Golgi apparatus is as important as any organelle in your cell.

References

Alberts, B., Johnson, A., Lewis, J., Raff, M., Roberts, K., & Walter, P. (2002). Molecular Biology of the Cell (4th ed.). Garland Science. ISBN: 0-8153-3218-1

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Alberts, B., Bray, D., Hopkin, K., Johnson, A. D., Lewis, J., Raff, M., Roberts, K., & Walter, P. (2013). Essential Cell Biology (4th ed.). Garland Science. ISBN: 978-0815344544.

Hua Z, Graham TR. The Golgi Apparatus. In: Madame Curie Bioscience Database [Internet]. Austin (TX): Landes Bioscience; 2000-2013. Available from: https://www.ncbi.nlm.nih.gov/books/NBK6268/

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The Editors of Encyclopaedia Britannica. (n.d.). How was the Golgi apparatus discovered? | Britannica. Encyclopedia Britannica. https://www.britannica.com/question/How-was-the-Golgi-apparatus-discovered